package cn.flightfeather.thirdapp.view;
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import android.content.Context;
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import android.content.res.Resources;
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import android.graphics.Canvas;
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import android.graphics.Color;
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import android.graphics.Paint;
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import android.graphics.Rect;
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import android.graphics.Typeface;
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import android.support.v7.widget.RecyclerView;
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import android.text.TextPaint;
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import android.util.Log;
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import android.view.View;
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import cn.flightfeather.thirdapp.R;
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/**
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* 2018.11.07
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* @author riku
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* recyclerView的分组标题
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*/
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public class SectionDecoration extends RecyclerView.ItemDecoration {
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private static final String TAG = "SectionDecoration";
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private DecorationCallback callback;
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private TextPaint textPaint;
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private Paint paint;
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private int topGap;
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private Paint.FontMetrics fontMetrics;
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public SectionDecoration(Context context, DecorationCallback decorationCallback) {
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Resources res = context.getResources();
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this.callback = decorationCallback;
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paint = new Paint();
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paint.setColor(res.getColor(R.color.colorAccent));
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paint.setAlpha(0);
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textPaint = new TextPaint();
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textPaint.setTypeface(Typeface.DEFAULT_BOLD);
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textPaint.setAntiAlias(true);
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textPaint.setTextSize(26);
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textPaint.setColor(Color.BLACK);
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textPaint.getFontMetrics(fontMetrics);
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textPaint.setTextAlign(Paint.Align.LEFT);
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fontMetrics = new Paint.FontMetrics();
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topGap = res.getDimensionPixelSize(R.dimen.sectioned_top);//32dp
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}
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@Override
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public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
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super.getItemOffsets(outRect, view, parent, state);
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int pos = parent.getChildAdapterPosition(view);
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Log.i(TAG, "getItemOffsets：" + pos);
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long groupId = callback.getGroupId(pos);
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if (groupId < 0) return;
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if (pos == 0 || isFirstInGroup(pos)) {//同组的第一个才添加padding
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outRect.top = topGap;
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} else {
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outRect.top = 0;
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}
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}
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@Override
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public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
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super.onDraw(c, parent, state);
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int left = parent.getPaddingLeft();
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int right = parent.getWidth() - parent.getPaddingRight();
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int childCount = parent.getChildCount();
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for (int i = 0; i < childCount; i++) {
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View view = parent.getChildAt(i);
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int position = parent.getChildAdapterPosition(view);
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long groupId = callback.getGroupId(position);
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if (groupId < 0) return;
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String textLine = callback.getGroupFirstLine(position).toUpperCase();
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if (position == 0 || isFirstInGroup(position)) {
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float top = view.getTop() - topGap;
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float bottom = view.getTop();
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c.drawRect(left, top, right, bottom, paint);//绘制标题矩形
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c.drawText(textLine, left, bottom-topGap/2, textPaint);//绘制文本
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}
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}
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}
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private boolean isFirstInGroup(int pos) {
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if (pos == 0) {
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return true;
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} else {
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long prevGroupId = callback.getGroupId(pos - 1);
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long groupId = callback.getGroupId(pos);
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return prevGroupId != groupId;
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}
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}
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public interface DecorationCallback {
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long getGroupId(int position);
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String getGroupFirstLine(int position);
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}
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}
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